In a conventional embedded power supply, a printed circuit board (PCB) with multiple thick copper layers and a special process of surface-mounting power devices are usually employed to reduce the overall volume and increase the reliability. Consequently, the embedded power supply is widely used in wireless networks, fiber-optic network apparatuses, servers and data storage devices.
Generally, when a full-regulated converter is applied to the conventional embedded power supply, the efficiency of the full-regulated converter is restricted and fails to be effectively enhanced. For example, in the full-regulated converter, the output voltage from the power module is fed back and compared with a fixed reference voltage. According to the comparing result, a control module adjusts a driving signal. According to the driving signal, the output voltage of the power module is correspondingly adjusted. Consequently, the magnitude of the output voltage is determined according to the comparison between the fixed reference voltage and the feedback voltage. Moreover, for allowing the power module to generate a corresponding output voltage according to the input voltage, the turn ratio of the transformer of the power module should be very small. Consequently, at the minimum input voltage, the power module can still generate the output voltage corresponding to the fixed reference voltage. Under this circumstance, the power module can be operated in the full-regulated status. However, if the turn ratio of the transformer of the power module is too large, the power module fails to generate the output voltage corresponding to the fixed reference voltage. Under this circumstance, the feedback adjusting function of the power module according to the output voltage will be lost.
Due to the limitation of the turn ratio of the transformer, when the power module is operated at a high input voltage, the output inductor is usually subjected to a very high volt-second value (V×t). Consequently, the output inductor should have a large-sized magnetic core or more winding turns. Under this circumstance, the power density of the power module is limited and the power module fails to be enhanced.